Ok, I need a bit of help, since I don't have a a lot of clues on how to do this.
After six months, I'm trying to take some measurements. As I have mentioned some times, I weight between 57 and 58 kg (nearly underweight), and my measures are dictated by the bone, since I have no visible fat. This causes me to use rather weird sizes. L for tops, M when there are no sleeves, and between and S and an M for the lower part of the body. My underwear is a size 34, which pretty much seems to be my current hip size.
I'm going to use a photo of me, and I hope you don't mind the blurriness. I did not want to set the tripod, and I don't feel very well using a defined picture of myself in underwear.

I'm not that sure, but Have I picked the correct line to set it as hips? Because it feels so weird that the body contracts there instead of expanding.
BTW, The origin of this is that i was looking for a two piece swimsuit, and I don't know how to find the right size having so different measures (big chest, small hips) Maybe I need two buy two different sizes and merge them into one?
http://www.amazon.co.uk/Zicac-Swimwear-Swimsuit-Tankini-shopping/dp/B00DVFZG8M/ref=sr_1_16?ie=UTF8&qid=1382976537&sr=8-16&keywords=bikiniIf I look at the explained measures here, I would need an EU 34 for the bottom and an EU 40/42 for the top...